The RTX code asm_operands
represents a value produced by a
user-specified assembler instruction. It is used to represent
an asm
statement with arguments. An asm
statement with
a single output operand, like this:
asm ("foo %1,%2,%0" : "=a" (outputvar) : "g" (x + y), "di" (*z));
is represented using a single asm_operands
RTX which represents
the value that is stored in outputvar
:
(set rtx-for-outputvar (asm_operands "foo %1,%2,%0" "a" 0 [rtx-for-addition-result rtx-for-*z] [(asm_input:m1 "g") (asm_input:m2 "di")]))
Here the operands of the asm_operands
RTX are the assembler
template string, the output-operand's constraint, the index-number of the
output operand among the output operands specified, a vector of input
operand RTX's, and a vector of input-operand modes and constraints. The
mode m1 is the mode of the sum x+y
; m2 is that of
*z
.
When an asm
statement has multiple output values, its insn has
several such set
RTX's inside of a parallel
. Each set
contains a asm_operands
; all of these share the same assembler
template and vectors, but each contains the constraint for the respective
output operand. They are also distinguished by the output-operand index
number, which is 0, 1, ... for successive output operands.